USGS Volcano Notice - DOI-USGS-AVO-2026-03-20T19:13:05+00:00

ALASKA VOLCANO OBSERVATORY WEEKLY UPDATE
U.S. Geological Survey
Friday, March 20, 2026, 1:07 PM AKDT (Friday, March 20, 2026, 21:07 UTC)

GREAT SITKIN (VNUM #311120)
52°4'35" N 176°6'39" W, Summit Elevation 5709 ft (1740 m)
Current Volcano Alert Level: WATCH
Current Aviation Color Code: ORANGE

Lava continues to slowly erupt within the summit crater at Great Sitkin Volcano. Minor lava dome growth to the southwest and rockfalls down the south side of the dome were observed in rare clear satellite views. Elevated surface temperatures from the warm, active lava dome were also observed when conditions allowed. Seismic activity remains low, with the detection of occasional small volcanic earthquakes and seismic signals from small rockfalls within the crater.   

The current lava eruption began in July 2021 and has filled most of the summit crater and advanced into the valleys below. There have been no explosions at Great Sitkin Volcano since an event in May 2021. The volcano is monitored using local seismic and infrasound sensors, satellite data, and web cameras, and regional infrasound and lightning networks.

Great Sitkin Volcano is a basaltic andesite volcano that occupies most of the northern half of Great Sitkin Island, a member of the Andreanof Islands group in the central Aleutian Islands. It is located 26 miles (42 km) east of the community of Adak. The volcano is a composite structure consisting of an older dissected volcano and a younger parasitic cone with a ~1 mile (1.6 km)-diameter summit crater. A steep-sided lava dome, emplaced in the crater during an eruption in 1974, has been mostly buried by the ongoing eruption. The 1974 eruption produced at least one ash cloud that likely exceeded an altitude of 25,000 ft (7.6 km) above sea level. A poorly documented eruption also occurred in 1945, producing a lava dome that was partially destroyed in the 1974 eruption. Within the past 280 years a large explosive eruption produced pyroclastic flows that partially filled the Glacier Creek valley on the southwest flank.

SHISHALDIN (VNUM #311360)
54°45'19" N 163°58'16" W, Summit Elevation 9373 ft (2857 m)
Current Volcano Alert Level: ADVISORY
Current Aviation Color Code: YELLOW

Signs of volcanic unrest at Shishaldin Volcano continue. Seismic and infrasound activity remain elevated, with numerous small earthquakes, frequent infrasound signals, and volcanic tremor recorded throughout the week. Daytime web camera views and a high-resolution satellite view on March 19 showed minor steaming from the summit, and sulfur dioxide gas emissions were detected in satellite data all week.   

Shishaldin Volcano is monitored by local seismic and infrasound sensors, web cameras, and a telemetered geodetic network. In addition to the local monitoring network, the Alaska Volcano Observatory uses nearby geophysical networks, regional infrasound and lightning data, and satellite data to monitor the volcano. 

Shishaldin Volcano, located near the center of Unimak Island in the eastern Aleutian Islands, is a conical stratovolcano with a base diameter of approximately 10 miles (16 km). It is one of the most active volcanoes in the Aleutian volcanic arc, with at least 54 episodes of unrest, including over 28 confirmed eruptions since 1824. Most eruptions are relatively small, although activity during the 1999 and 2023 eruptions generated ash columns that reached up to 46,000 ft (16 km) above sea level.

ATKA VOLCANIC COMPLEX (VNUM #311160)
52°19'51" N 174°8'20" W, Summit Elevation 5030 ft (1533 m)
Current Volcano Alert Level: ADVISORY
Current Aviation Color Code: YELLOW

Low-level unrest continued at Atka volcanic complex with weak-to-moderate volcanic tremor, and numerous small earthquakes detected in seismic data. Clear satellite views over the week showed weak-to-moderately elevated surface temperatures for the Korovin summit lake region. Sulfur dioxide gas emissions were also detected in satellite data all week. 

The Atka volcanic complex is monitored by local seismic and infrasound sensors and webcam, satellite data, and regional lightning detection instruments. 

The Atka volcanic complex forms the northern part of Atka Island, located about 16 km north of the community of Atka and 1,761 km southwest of Anchorage. The Atka volcanic complex includes a possible older caldera and several younger vents, including Korovin Volcano, Mount Kliuchef, and Sarichef Volcano. Korovin Volcano, a 1553-m-high (5030 ft) stratovolcano, has been the site of most historical volcanic activity, and has a small, roiling crater lake that occasionally produces energetic steam emissions. Korovin has erupted several times in the past 200 years, including 1973, 1987, and 1998, and has likely had small ash emissions as recently as 2005. Typical recent Korovin eruptions produce minor amounts of ash and occasional but small lava flows. Reports of the height of the ash plume produced by the 1998 eruption ranged as high as 10,600 m (35,000 feet) above sea level. Mount Kliuchef is composed of a series of five vents aligned northeast–southwest. The two main summit vents of Kliuchef appear relatively young and the easternmost was probably the source of an 1812 eruption that is sometimes attributed to Sarichef.

CONTACT INFORMATION:

Matt Haney, Scientist-in-Charge, USGS mhaney@usgs.gov (907) 786-7497

David Fee, Coordinating Scientist, UAFGI dfee1@alaska.edu (907) 378-5460

Contact AVO: https://avo.alaska.edu/contact

The Alaska Volcano Observatory is a cooperative program of the U.S. Geological Survey, the University of Alaska Fairbanks Geophysical Institute, and the Alaska Division of Geological and Geophysical Surveys.